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<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>小熊圆饼图</title>
<meta charset="gbk">
<script>
//绘制饼图
function drawCircle(canvasId, data_arr, color_arr, text_arr) {
var c = document.getElementById(canvasId);
var ctx = c.getContext("2d");
var radius = c.height / 2 - 20; //半径
var ox = radius + 20,
oy = radius + 20; //圆心
var width = 30,
height = 10; //图例宽和高
var posX = ox * 2 + 20,
posY = 30; //
var textX = posX + width + 5,
textY = posY + 10;
var startAngle = 0; //起始弧度
var endAngle = 0; //结束弧度
for (var i = 0; i < data_arr.length; i++) {
//绘制饼图
endAngle = endAngle + data_arr[i] * Math.PI * 2; //结束弧度
ctx.fillStyle = color_arr[i];
ctx.beginPath();
ctx.moveTo(ox, oy); //移动到到圆心
ctx.arc(ox, oy, radius, startAngle, endAngle, false);
ctx.closePath();
ctx.fill();
startAngle = endAngle; //设置起始弧度
//绘制比例图及文字
ctx.fillStyle = color_arr[i];
ctx.fillRect(posX, posY + 20 * i, width, height);
ctx.moveTo(posX, posY + 20 * i);
ctx.font = ‘bold 12px 微软雅黑‘; //斜体 30像素 微软雅黑字体
ctx.fillStyle = color_arr[i]; //"#000000";
var percent = text_arr[i] + "：" + 100 * data_arr[i] + "%";
ctx.fillText(percent, textX, textY + 20 * i);
}
}
function init() {
//绘制饼图
//比例数据和颜色
var data_arr = [0.2, 0.3, 0.3, 0.2];
var color_arr = ["#FFAA00", "#00AABB", "#73BF00", "#FF4400"];
var text_arr = ["NO1", "NO2", "NO3", "NO4"];
drawCircle("canvas_circle", data_arr, color_arr, text_arr);
}
//页面加载时执行init()函数
window.onload = init;
</script>
</head>
<body>
<p>
<canvas id="canvas_circle" width="500" height="300" style="border:2px solid #5A5AAD;">
浏览器不支持canvas
</canvas>
</p>
</body>
</html>
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原文地址：http://www.cnblogs.com/ludarong/p/5280219.html
